Scattering and Polarimatric Components in Community Radiative Transfer Model Quanhua (Mark) Liu The 4 rd JCSDA Science Workshop, May 31- June 1, 2006, Camp Springs, MD F. Weng, Y. Han, P. van Delst, R. Treadon, J. Derber at JCSDA

Important Components in CRTM Versatile transmittance models (OPTRAN, OSS) Cloud scattering and absorption Advanced surface emissivity models (NESDIS, FASTEM) Various solvers for radiative transfer equations Infrared and Microwave Sensors Module platform to incorporate new research and education components

Radiative Transfer Model Radiative transfer solver is one of the key components of CRTM. Delta 4 stream vector radiative transfer model – (UCLA) Direct ordinate tangent linear radiative transfer (DOTLRT) - NOAA/ETL Successive Order of Iteration (SOI) – Uni. Wisc. Advanced Doubling-Adding Method (ADA) – NOAA/STAR Many other models, such as: CIRA/CU – SHDOMPPDA, two-stream model (Schmetz), Eddington approximation (Kummerow), and a linearized discrete ordinate radiative transfer model (Spurr et al.).

ADA Method Layer transmission and reflection Layer source function Vertical integration the surface reflection matrix, loop k from n  1 TOA radiance

Remark Numerically exactly Analytical expressions replace the most complicated terms: source functions. F90/F95 matrix and vector manipulation makes coding simple, also simple for tangent-linear and adjoint coding, good for code maintenance Add a viewing angle in the streams for satellite radiance Fast, about 60 times faster than the original double-adding method Easy extension, for example: Double the size of vector and matrix dimension and other minor change for the atmospheric residual polarization (completed) Add a sun angle in the streams and add a loop over azimuthal-component for visible/UV radiance simulation (working)

Comparison, 23.8 GHz A rain cloud having an effective radius of 200 microns and 0.5 mm water content was put at 850 hPa. One layer ice cloud having the same effective particle size and 0.1 mm ice water path is located at 300 hPa Zenith angleADA VDISORTDA

Comparison, 10.8 micron An ice cloud having an effective particle size of 20 microns and 0.1 mm ice water path was located at 300 hPa and a liquid water cloud at 850 hPa having an effective particle size of 10 microns and 0.5 mm are chosen. Zenith angleADA VDISORTDA

Phase Function Model Rayleigh function: molecular scattering (1871) Henyey-Greenstein: approximate scattering (1941) for particles having finite size, no polarization. HG-Rayleigh scattering matrix The normalization factor C and the asymmetry factor G used in HG part in HG-Rayleigh can analytically derived from (1) (2) (3)  ---  G=f(g)

Test HG-Rayleigh Scattering Matrix in CRTM Many thanks to Prof. Liou’s group to provide phase coefficients using finite-difference time domain method. g=0.027 r=90 micron

Test HG-Rayleigh Scattering Matrix in CRTM g=0.27 r=276 micron

WINDSAT Polarimetric Measurements Stokes components (IR/MW) Intensity: surface/atmosphere and space emission Polarization: surface emission /reflection, atmospheric scattering The third and the fourth Components: discontinuity /roughness of surfaces, 3D effect, non-spherical scatterers

New Measurements and Challenge Clouds, ice edge, sea ice, clearly delineates water/land and water/ice boundaries. Geographic data NOT used!!!

3D Radiative Transfer Simulation, emissivity=1 U component contributed from 3D effect only for spherical scatterers.

Simulation and Measurement Simulations for BonnieWindsat observation for Isabel The third Stokes parameter from Windsat observations of 3 rd Stokes parameter clearly reveals the vortex structure of surface wind.

Radiances in Studying Hurricane (Warm Core from SSMIS Observations at 54.4 GHz) The SSMIS measures radiances in 24 channels covering a wide range of frequencies (19 – 183 GHz) conical scan geometry at an earth incidence angle of 53 degrees maintains uniform spatial resolution, across the entire swath of 1700 km.

Due to the limb effect, warm core is no longer observable. CRTM is needed for quantitatively analysis. AMSU-A Radiances at 54.4 GHz, CRTM needed to remove the Limb Effect

Applying the limb adjustment developed by Dr. Goldberg et al. (2001), AMSU-A 54.4 GHz can show the warm core of Katrina. Limb Correction

Discussion ADA mathematically elegant and coding is simple. It is fast (60 times faster than original double-adding) Can be easily extend including visible/UV (use sun zenith as an additional stream and one loop over azimuth components) New HG-Rayleigh is a good approximation for cloud scattering in MW and aerosol scattering in IR. Polarimetric ocean model available, but lack of the polarimetric snow/ice models.